As railroads push to increase car capacity to handle the increasing demands on the transportation network, freight car designers/builders have been stepping up to the challenge. With the overall train lengths limited by system constraints such as passing siding lengths, the challenge has been how to achieve more railcar capacity in the same or shorter lengths of freight cars and trains. Freight car designers/builders have heretofore met this challenge by pushing the top and bottom of the defined clearance line envelopes to the limits allowed by the Association of American Railroads (the “AAR”). Additionally, car designers/builders have utilized modern design tools to make freights car designs lighter in weight, while still meeting the AAR standard design loads whereby allowing each freight car to carry more lading while maintaining maximum allowable gross rail loads.
During the process of assembling or “making-up” a freight train, railcars are run into and collide with each other to couple them together. Since time is money, the speed at which the railcars are coupled has significantly increased. Moreover, and because of their increased capacity, the railcars are heavier than before. These two factors and others have resulted in increased damages to the railcars when they collide and, frequently, to the lading carried within such railcars and to the railcar itself.
As railroad car designer/builders have reduced the weight of their designs, they have also identified a need to protect the integrity of the railcar due to excessive longitudinal loads being placed thereon, especially as the railcars are coupled to each other. Whereas, such longitudinal loads frequently exceed the design loads set by the AAR. Providing an energy absorption/coupling system at opposed ends of each railcar has long been known in the art. Such a system typically includes a draft assembly comprised of a coupler for releasably attaching two railcars to each other and a draft gear assembly arranged in operable combination with each coupler for absorbing, dissipating and returning energy imparted thereto during make-up of the train consist and during operation of the railcar.
The draft gear assembly is typically disposed within a pocket defined by a centersill on the railcar and has an operative length of travel in one direction of movement of about 3.5 inches before solid stops limit the travel and no more energy can be absorbed by the draft gear. Over this limited distance, the energy of the moving railcar must be absorbed so as to reduce the impact forces and resulting damage to the adjacent railcar to be coupled thereto. Largely because of their increased coupling speeds and the increased weights of the loads being carried thereby, heretofore known energy absorption/coupling systems have been shown to be inadequate. As such, railcars are experiencing severe end-impacts that can cause a complete collapse of the end of the car—resulting in large repair costs—coupled with damage to the lading—resulting in significantly higher insurance premiums.
Increasing the travel of the draft gear assembly would advantageously allow more energy to be absorbed. The challenge of increasing the travel of the draft gear assembly is, however, complicated. Increasing the travel of the draft gear assembly has heretofore meant increasing the length of the railcar to accomplish such a beneficial result. The length of a railroad car, however, is critical.
Passing sidings and loading facilitates often limit the number of railcars that can be joined to each other in one train. Lengthening each energy absorption/coupling system even by about 3 inches would add almost 50 feet to the cumulative or overall length of a 100 railcar train consist. This would result in the last railcar in such a 100 car consist no longer fitting on the siding and, thus, having to be left behind. As such, there would be at least a one percent (1%) loss in train efficiency. This is simply unacceptable. Accordingly, the concept of increasing the length of each energy absorption/coupling system can be accepted only in limited, special purpose applications.
Thus, there is a continuing need and desire for an energy absorbing/coupling system for a railcar which allows for increased travel over which the high level of energy from impact loads of colliding railcars can be absorbed, dissipated and returned while maintaining the length of the draft gear assembly housing constant with known housing designs along with a method for coupling two railcars to each other.